- PADI - The Professional Association of Diving Instructors (PADI) is the world's largest recreational diving membership and diver training organization founded in 1966 by John Cronin and Ralph Erickson. Cronin was originally a NAUI instructor who decided to form his own organization with Erickson, and to break diver training down into several modular courses instead of the single universal course then prevalent. PADI courses range from minimal entry level to relatively advanced recreational diver certification, several specialized diving skills courses, usually connected with specific equipment or conditions, some diving related informational courses and a range of recreational diving instructor certifications.
- SSI - Scuba Schools International (SSI) is an organization that teaches the skills involved in scuba diving and freediving, and supports dive businesses and resorts. SSI has over 2,500 authorized dealers, 35 regional centers, and offices all over the world. SSI offers internationally recognized recreational diver training programs - starting with snorkeling and entry level scuba diving courses up to Instructor Certifiers. The most common programs are: SSI Open Water Diver (OWD), Advanced Open Water Diver (AOWD). There are more than 30 different specialty courses. Dive leader training programs start with the Dive Control Specialist (who is qualified like Assistant Instructor) followed by Open Water Instructor and above. SSI's training program for children aged 8–12 years is called Scuba Rangers. The training program for technical divers is called TechXR (Technical Extended Range) and includes decompression diving, trimix and other courses that exceed the limit for recreational divers.